CENTRIFUGAL FAN WITH IMPROVED CUT OFF MEANS

摘要

A centrifugal fan having a fan wheel with a fluid inlet at the rotational axis of the fan wheel and a discharge outlet spaced radially outwardly of the inlet in a plane substantially parallel to the axis is provided with increased efficiency and discharge flow by controlling the flow of fluid across a cut off means which peels fluid from the fan wheel for discharge through the outlet. More specifically, some of the fluid moving across the cut off means is withdrawn therefrom through a passageway extending to a region of lower pressure to reduce the thickness of a fluid boundary layer at the cut off means and thereby provide an increased cross sectional area with decreased frictional losses. Preferably, the withdrawn fluid is recirculated within the centrifugal fan.